[Bug target/21389] optimized code seg faults due to double load on sparcV9

["drew dot johnson at andrew dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From drew dot johnson at andrew dot com  2005-05-06 19:47 -------
Subject: RE:  optimized code seg faults due to double load on sparcV9

Then what is the point of the -munaligned-doubles flag?  Is this simply
ignored?  I understand your point about malloc, but what if we have
casts to buffers that are not mod8-aligned?  Isn't that what
-munaligned-doubles is for? 

I am going back over the original code to find out how we are allocating
the data struct that is causing my program to fail.  I will let you know
when I find something more.

Drew

-----Original Message-----
From: pinskia at gcc dot gnu dot org [mailto:gcc-bugzilla@gcc.gnu.org] 
Sent: Friday, May 06, 2005 3:08 PM
To: Johnson, Drew
Subject: [Bug target/21389] optimized code seg faults due to double load
on sparcV9


------- Additional Comments From pinskia at gcc dot gnu dot org
2005-05-06 19:07 -------
(In reply to comment #4)
> Subject: RE:  optimized code seg faults due to double load on sparcV9
> 
> I don't think so.  Malloc does not guarantee anything but mod-4
> alignment.  You have to use memalign to get something better (at least
> on a Sun).  I only did the +4 pointer stuff to ensure that the double
> would be misaligned mod8, as this is what was happening in my code.
As
> long as I am on a mod4 boundary for my struct, the -munaligned-doubles
> flag should force the handling of doubles as though they are
unaligned.
> The compiler with no optimization does this.  But as soon as you turn
on
> -O1, it ignores the unaligned-doubles directive.

Again what you said about malloc is not true and has not been true since
1989.
The C standard says malloc aligns things the largest alignment required
for that machine.  In this case 
doubles are aligned by 8.  So your code is invalid.

-- 
           What    |Removed                     |Added
------------------------------------------------------------------------
----
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21389

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21389